Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 56
Fig. 118. nut and washer. The loose stock is useful for drawing parallel lines obliquelyto the edges of the board, such as the threads of screws, oblique columns, orconnecting-rods of steam-engines. T squares are also made with a single movable head, shown in Fig. 119; «« … Figs. 119,120. the blade, turning on «, is clamped in position by the thumb-nut h. Fig. 120illustrates a T square wdth a protractor at the head, convenient for laying offlines of designated angles. In many drawing-cases will be found the parallel ruler (Fig. 121), consist-
Mechanical drawing
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